Russell's Viper

Daboia russelii

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The Russell's viper (Daboia russelii) a venomous Old World viper, is found throughout Asia, in the Indian subcontinent, much of Southeast Asia in southern parts of China and Taiwan. The species is found in many countries India, Pakistan, Sri Lanka, Myanmar, Bangladesh, Nepal, Thailand, Cambodia, China, Taiwan and Indonesia

It's genus, Daboia is monotypic, meaning it only comprises a single species, and the name derives from the Hindi word meaning "the lurker" or "that lies hid". The Russell's viper is also known by several other common names like Daboia, chain viper, Indian Russell's viper, common Russell's viper, chain snake, scissors snake and seven pacer.

The species was named in after Patrick Russell (1726–1805), the Scottish herpetologist that first described many of the Indian snakes. The Russell's viper is a member of the big four snakes of India, and it's also the snake species responsible for the most snakebite incidents and deaths among all venomous snakes.

The Eastern russell's viper (Daboia siamensis) is considered a subspecies, although it's also sometimes treated as a full species. It's found in Taiwan, southern China, Myanmar, Thailand, Cambodia, Indonesia.​

These are large snakes with an average length of about 4 feet (120 cm) on the mainland Asian populations, and a maximum length of around 5.5 ft (1.7 m), island populations are smaller in size.

The Russell's viper head is and distinct from the neck with a long, flattened and triangular shape, and large, conspicuous nostrils on each side of the snout. The background color may vary from dark brown, brownish-yellow to a brownish-gray, with a dorsal pattern consisting of 3 rows of black or brown oval spots with black, white, or both edges.

Sometimes the spots in middle fuse together to form more of a zigzag pattern. Juvenile specimens are usually brownish-orange to clear orange. They have large fangs up to 0.65 inches (16.5 mm) and a short tail.

Russell's viper isn't restricted to any particular habitat, but it's most commonly found in plains, coastal lowlands, savannahs, foothills on montane areas or hills with suitable habitats. The species does tend to avoid densely forested areas and is mostly found in open, grassy or bushy areas, but can also be found in scrub jungles, forested plantations and farmlands.

These snakes also avoid humid habitats like marshes, swamps or rain forests. They are also uncommon at higher altitudes, but specimens have been reported up to 7500 to 9800 feet (2300-3000 m).

The Russell's viper will take shelter in rodent burrows, old termite mounds, rock crevices, piles of leaves, or other debris. They are also found near human dwellings in search of prey, but not as common as the cobras or kraits.

These snakes are terrestrial and primarily nocturnal, especially during hot weather. However, in the event of cool weather, they will change their behavior and become more active during the day.

Adult snakes are somewhat slow and sluggish, but if pushed beyond their limit they can become very aggressive. On the other hand, juveniles are generally much more nervous. When disturbed Russell's viper forms a series of "S" shaped loops raising one-third of the body and will hiss loudly.

Venom / Bite

These are strong snakes that may react violently to being picked up, if a bite does occur it may be a snap, or the snake may hang on for several seconds. When the snake strikes it can exert so much force that even a large specimen may lift most of its body off the ground.

The quantity of venom produced by the russell's viper is considerable, with adult specimens injecting from 130 mg to 268 mg in a single bite. Necrosis isn't usually very deep and stays limited to the area of the bite, but in some cases, it may be severe.

When bitten, humans will experience a wide variety of symptoms including pain, blistering and swelling at the bite location, bleeding (especially from the gums), vomiting, dizziness, blood in-coagulability and kidney failure.

With early medical treatment and access to the antivenom, the severe or potentially lethal complications are drastically reduced. From the russell's viper bite survivors, a third will suffer severe damage to their pituitary glands, resulting in hypopituitarism.

Diet / Feeding

The russell's viper feeds primarily rodents and small mammals, especially murid species, they also feed on squirrels, shrews, land crabs, scorpions, birds, lizards or frogs.

The juvenile specimens are crepuscular, and forage actively feeding mainly on lizards, but are also known to be cannibalistic.

The prey is stalked and then bitten and released when it dies the snakes eats it. As the snake grows and becomes an adult, it specializes in rodents, in fact, the main reason they are attracted to human settlements is the presence of rodents and lizards.

Reproduction

The russell's viper is ovoviviparous, producing eggs that hatch inside the body and the young are born alive. The sexual maturity is achieved in about 2 to 3 years, and the minimum length for a pregnant female snake is about 39 inches (100 cm).

The species is a very prolific breeder, and litters of 20 to 40 offspring are common, although there may be one hatchling in a litter the recorded maximum is 65 from a single litter. At birth, the juveniles measure around 8.5 to 10.2 inches (215 to 260 mm).

The breeding season generally occurs early in the year extending from April to July, although gravid females may be found up to September. The Russell's viper gestation period lasts more than 6 months, and the young are born from May to November, but mostly in the months of June and July.​Conservation / Threats

The 2 most common threats to the Russell's viper snake species are roadkill mortality, and humans killing it out of fear due to their venom potency and aggression when they encounter humans. They are also killed for their skin and meat.

Their venom is also illegally traded in parts of its range, for various uses including medical and research use. The species is listed as "Least Concern" by IUCN, as it's highly adaptable and widespread and abundant in human-modified habitats.